Let me try to sell you on the Terror
(Full disclosure, I owned the Orange for a couple months before switching to the Aguilar Tone Hammer - just better for what I do, IMHO. If I was doing anything at all more aggressive, I'd still have it. Also, I haven't played any of the other heads mentioned here. So there, throw my opinion out if you must

)
Orange Terror are some cool heads but they are probably not what you want if you are looking for clean power.
For clean power, just keep the gain down. Plenty of room on the master. There's also an input pad for further preamp headroom. And the dirty power? Well it sounds AWESOME if you want it. You said you play metal? Yeah, you could probably stop reading here and go buy it
Budget right now isn't huge, however, if you suggest that something that is worth it, I could spend the time saving up for it. I just want to know what some good suggestions would be nonetheless. So maybe suggesting a few things across a few price ranges would be helpful too.
These pop up once and a while as refurb units for $100 or so less than typ. (I'm typing this on a refurb MacBook from 2006, still going strong for $200 less!)
Why is the switchable 8 ohm/4 ohm knob so appealing? Do you have an extra cab you're not telling us about? It is my understanding that your cab runs at 8 ohms so you wouldn't need a 4 ohm load. Not that it matters; I haven't heard of a head that doesn't handle a 4 ohm load.
The switchable 8/4 ohm knob is pretty standard practice in the sense that virtually all heads run safely at 8 and 4 ohms.
Edit: I have heard that the Orange Terror's signal is very scooped. You may want to take that into account if that's not your thing, especially considering that your current head doesn't seem to be delivering the power you need. Scooped equalizing gives nice drive to your tone but it tends to bury you in the mix.
These are all great points. If you haven't, read the BGM review (
Link Removed) it explains a lot. As for the ohm switching, all that is is a switchable limiter so that more juice can be put out (with a slight increase in %THD) to achieve a true 500W@8ohm or the stock 500W@4ohm. This means you can get the same power as a typical 1000W@4ohm head. Keep in mind though, 2x power = 3dB increase in "loudness." More, yes, but typically a bit underwhelming. And about the scooped'ness, the EQ is baked to be flat when L-M-H are at all the way down-all the way up-all the way down. Again, once you know that, it's easier to stay away from Scoopsville, UK.
Finally, if you hear with your eyes (not that there's anything wrong with that!), have you seen a cooler looking head?

